This invention relates to an intrapericardial assist device. This invention also relates to a method for assisting a patient's heart in its pumping function.
When a patient's heart stops, for example, in the operating room, cardiopulmonary resuscitation (CPR) is required. In that procedure the chest is violently pounded at the region of the sternum to compress the chest and thereby compress the heart between the sternum and the spine. This compression forces blood out of the ventricles through the one-way valves of the heart. When the pressure on the heart is released, the heart expands and blood is sucked into the heart.
For all its violence, CPR is a delicate procedure in that it must be performed correctly in order to have the desired result of starting the stopped heart. A problem with CPR is that, whether or not it is performed correctly, CPR invariably results in cracked ribs, a fractured sternum and destroyed costochondral (cartilage) junctions. Thus even if a patient survives CPR, he is usually injured.
Another serious cardiac condition arises in people who have experienced heart attacks. In such persons, a portion of the heart muscle is frequently destroyed by the attack. Although nerves passing through the damaged heart tissue are not destroyed to the point of ceasing function, the operation of the nerves may be significantly impaired. Conduction of nerve impulses may be delayed. This delay in signal transmission over the impaired nerves results in a delay in heart muscle contraction in those parts of the heart controlled by the impaired nerves. This condition is observed as a "bundle branch block" in an electrocariogram.
Another abnormal and detrimental cardiac condition is a hypertrophy of the left ventricular muscle owing to a sticky heart valve or aortic stenosis. The increase in left ventricular pressure resulting from increased resistance to blood flow out of the left ventricle gradually induces an increase in the size of the myocardium about the left ventricle. This left ventricular hypertrophy is a dangerous condition, particularly where the individual suffers from coronary artery disease. The larger heart muscle requires greater blood flow and is therefore more sensitive to even temporary reductions in that flow. Such a reduction in blood flow occurs, for example, when the afflicted individual exercises.